High Performance Glad Nanorod CuInxGa(1-x) Se2 Arrays with Enhanced Carrier Collection and Light Trapping for Photodetector Application

Nanostructured arrays have become an appealing alternative to their thin film and bulk counterparts in photovoltaic and photoconductivity applications. Thin films have recently continued the evolution of efficiency and material sciences after taking over from traditional, doped silicon devices. Inside of the thin film revolution, CuInxGa(1-x)Se2 (CIGS) has emerged as a high efficiency p-type semiconductor with a wide band gap that is tunable based on the Indium to Gallium ratio and often deposited via expensive, high temperature deposition methods. While each of the aforementioned methods of construction have their disadvantages, the advantages of each can be combined to potentially increase the efficiency and performance of a photodetector.;While the community at large has been concentrating on developing low defect, high efficiency absorbers, nanorod arrays have become a promising substitution due to their fundamentally lower mass loading and increased optical absorption in comparison to their thin film counterparts. Nanorod arrays also exhibit unique p-n junction geometries under varying anode/cathode geometries. The highest efficiency devices are often created using chemical vapor deposition, an energy intensive and high temperature method. RF/DC sputtering using a quaternary target in concert with glancing angle deposition (GLAD) creates relatively low energy, low temperature, self-assembling CIGS nanorod arrays.;The principle goal of this project is to investigate the optical absorption and charge carrier collection properties of CIGS nanorod arrays deposited via glancing angle deposition using a quaternary sputtering target for low cost and high performance photodetectors. Characterization techniques will include scanning electron microscopy (SEM), ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy, and time resolved photocurrent measurements via an illumination and source meter (SMU). Energy dispersive spectroscopy (EDS) and quartz crystal microbalance (QCM) are also used to study composition and mass loading of the CIGS samples and devices.;GLAD nanorod arrays of increasing lengths were fabricated to study the optical absorption performance versus optical path length of the absorber material. Thin films were also grown to the same thicknesses to benchmark all performance parameters. A noticeable shift in optical characteristics was observed between the deposited nanorods and their thin film counterpart by means of UV-Vis-NIR spectroscopy.;Finally, three different photoconductive device types of three increasing thicknesses (nine constructions in total) were made of an indium tin oxide anode, a CuIn0.7Ga0.3Se2 main absorber layer, and a silver (Ag) cathode to investigate charge carrier collection. Time resolved photocurrent profiles of nanostructured photodetectors reveal that a moderately thick "capped" cathode nanorod array device performs better than the thickest traditional thin film configuration, but also better than any of the conformally coated absorber layers manufactured for this project providing exceedingly fast and high gain photodetection despite the limitations of geometry and fabrication.